The present invention relates to an improved implant for fixing dental prostheses.
It is known that implants for fixing dental prostheses substantially constituted by an intrabony section that is fixed upon assembly inside the bony part of the gum are currently particularly appreciated owing to their biotechnological characteristics.
A superstructure for anchoring the prosthesis is fixed to the intrabony section and is constituted by an abutment provided with an axial through hole accommodated in a seat formed in the intrabony section and suitable to provide the support around which the tooth is formed.
The superstructure normally also comprises an abutment fixing pin that is inserted axially in said abutment and is provided with a threaded portion that is associated, upon assembly, with a threaded blind hole formed axially in the bottom of said seat.
Currently, the coupling of said seat, which usually has a polygonal profile, particularly a hexagonal one, occurs by means of a complementarily shaped shank formed in said abutment.
However, these polygonal couplings between the intrabony section and the superstructure do not ensure perfect stability of the tooth, particularly in relation to rotation-preventing and extrusion-preventing functions.
It is in fact known that a tooth, during mastication, is subjected to intense mechanical stresses that require stable lockings and the total absence of mutual rotations between the dental prosthesis and the gum, on penalty of a drastic reduction of the functionality of said dental prosthesis, with considerable associated discomfort for the individual.
For this purpose, an implant has been devised which is disclosed in Italian patent No. 1288004 of Dec. 5, 1996 and is constituted by an intrabony section that is fixed, upon assembly, within the gum and to which a superstructure for anchoring the prosthesis is fixed.
Said structure is constituted by an abutment, which is provided with an axial through hole, is partially accommodated in a seat formed in said intrabony section, and is suitable to provide the support around which the tooth is constituted, and by an abutment fixing pin, which is inserted axially therein and has a threaded portion associated upon assembly with a threaded blind hole formed axially in the bottom of said seat.
Said seat has a portion that has a substantially triangular cross-section with radiused vertices and is coupled, upon assembly, to a complementarily shaped portion of a shank formed in the abutment element so as to provide, as a whole, a rotation-preventing and extrusion-preventing connection between the intrabony section and the superstructure.
The seat and the shank are also complementarily shaped and provided with a hexagonal cross-section in their remaining parts.
Although the cited implant constitutes an undisputed improvement with respect to the known art, since it provides total safety in the coupling between the intrabony section and the superstructure without the risk of mutual axial rotations thereof, said implant has shown in practice a considerable drawback that has prevented its diffusion.
Because of the hexagon-to-hexagon coupling combined with the triangle-to-triangle coupling, whose radiused vertices correspond to three alternated sides of the corresponding hexagons, during installation of the abutment, which is mostly performed without direct viewing, there is a 50% chance of choosing the incorrect mutual coupling position.
Accordingly, there is a 50% chance of fixing the implant badly, with consequent inconvenience and problems for the patient.
The aim of the present invention is to provide an implant for fixing dental prostheses to the gum that totally solves the problem noted above in the implant related to patent 1288004.
Another object of the present invention is to provide an implant whose structure is particularly easy to apply to the bony part of the gum and has, in its active configuration, high functionality and compatibility with the requirements of the individual.
Another object of the present invention is to provide an implant having a high degree of biocompatibility and suitable to simplify fitting on the part of the operator.
Another object of the present invention is to provide an implant whose costs are furthermore competitive with those of known implants.
Another object of the present invention is to provide an implant that can be manufactured with known technologies.
This aim and these and other objects that will become better apparent hereinafter are achieved by an improved implant for fixing dental prostheses, of the type constituted by an intrabony section that is fixed, upon assembly, within the bony part of the gum, and to which a tooth anchoring superstructure is fixed, said superstructure being constituted by an abutment provided with an axial through hole that is partially accommodated in a seat formed in said intrabony section and suitable to provide the support around which the prosthesis is constituted, and an abutment fixing pin that is inserted axially in said abutment and is provided with a threaded portion that is associated, upon assembly, with a complementarily threaded blind hole formed axially in the bottom of said seat, said seat having a portion provided with a triangular cross-section with radiused vertices and coupled, upon assembly, to a complementarily shaped portion of a shank formed in the abutment element, said implant being characterized in that said seat and said shank are complementarily shaped and provided with a circular cross-section in their remaining parts as well.